Is a planet's crust distinct from mantle because ....

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the mantle was formed at the beginning of the star system's evolution whereas the crust is sprinkled with far-flung stardust from faraway explosions? I ask this question because I had read that the collapse of a pair of neutron stars is what generates all the element with Z past the low-binging-energy Fe, shooting out matter at extraordinary speeds that can make it reach all systems in the galaxy, and the mantle is elements with Z lower than iron that are not the heaviest, which makes it down to the core (i.e., Fe, Ni).
 

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swampwiz said:
the mantle was formed at the beginning of the star system's evolution whereas the crust is sprinkled with far-flung stardust from faraway explosions?

No, essentially the entire Earth is formed of the materials already present in the gas and dust cloud that collapsed to form the solar system. Prior to the collapse, this cloud was seeded with heavy elements (heavier than hydrogen and helium) by material thrown out into interstellar space from various events, including supernovas, in the preceding eras. No significant amounts of heavy elements from outside the solar system have been picked up by the Earth since its formation.
 
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The Earth's crust is distinct from its mantle for two reasons:
  • It is colder and under lower pressure.
  • Less dense minerals have separated out from more dense ones over the Earth's history, making aluminum-silicate continents atop magnesium-silicate lower crust, oceanic crust, and mantle.
 
The reason that mantle and crust are different is largely due to the fact that the majority of our planet is liquid. Inside of a liquid, dense materials sink and light ones float. Billions of years ago, the materials in the Earth settled and the lighter materials rose to the surface where they froze like ice over a pond.
 
swampwiz said:
the mantle was formed at the beginning of the star system's evolution whereas the crust is sprinkled with far-flung stardust from faraway explosions? I ask this question because I had read that the collapse of a pair of neutron stars is what generates all the element with Z past the low-binging-energy Fe, shooting out matter at extraordinary speeds that can make it reach all systems in the galaxy, and the mantle is elements with Z lower than iron that are not the heaviest, which makes it down to the core (i.e., Fe, Ni).
Then what you read is incorrect (or you misunderstood it)
https://www.physicsforums.com/threa...-kilonovas-vs-supernovas.930258/#post-5875259